The main characteristic of a UWB based wireless communication system is the fact that it operates as an underlay system in frequency bands already in use by other wireless communication and location systems, such as RADAR. These systems will generate interference in UWB systems (in band interference), and the UWB system will generate interference towards these systems. Due to the very limited transmission power of the UWB systems, the range in which the generated interference will cause a degradation in the system is limited to some meters or a few tenths of a meter. A system operating in this area will also generate interference towards the UWB system in operation. This leads to a degradation of the communication performance.
Devices may operate according to the Ultra Wide Band (UWB) standard based on Orthogonal Frequency-Division Multiplexing (OFDM), called Multiband OFDM Alliance (MBOA). These devices can generate interferences toward a Worldwide Interoperability for Microwave Access (WIMAX) device.
OFDM is a method of digital modulation in which a signal is split into several narrowband channels (sub-carriers) at different frequencies. A WIMAX device operates, for example, with a bandwidth of 20 MHz at a central frequency of 3.5 GHz, whereas the frequency band of the MBOA system lies between 3.1 and 5.0 GHz.
Wireless personal area networks based on OFDM and UWB technologies like the MBOA standard will directly interfere with narrowband interferers which are close to such wide band devices. At present, no specific interference mitigation techniques are implemented in the UWB standard based on OFDM (MBOA).
To avoid in band spectral interference, WO 2005/006698 (INTEL) proposes to puncture, i.e., remove, selected sub-carriers. More precisely, this puncturing is made after the OFDM modulation in the transmitter while taking into account channel knowledge. Depuncturing is performed in the receiver before the OFDM demodulator. However, such a band dropping approach leads to a reduction in available bandwidth.